Nenjiang River grassland is an expansive low lying grassland drained by the Nenjiang and Songhua Rivers of China. The Nenjiang River originates among low hills that define China’s northeastern border with the Russian Far East. After winding through a series of valleys, the Nenjiang River flows down onto the Songhua-Nenjiang plain where flooded grasslands have historically provided important summer breeding habitat for a variety of migratory birds including six of the world’s fifteen crane species. The Red-crowned Crane, White-naped Crane, Siberian Crane and Demoiselle crane breed in this ecoregion, while the Common Crane and Hooded Crane stage here prior to migrating to their breeding habitat. Overfishing and agricultural development threaten the bird populations of this species-rich ecoregion.

Location and general description

Nenjiang River grassland is an expansive low lying grassland drained by the Songhua River of China. The rich soils have led to intensive agricultural exploitation, and the ecoregion also suffers from overfishing. The basin of the Nenjiang River is enclosed by low mountains, the Large Hinggan to the west and the Little Hinggan to the north. Higher mountains that form the base of the Korean Peninsula define the southern margin of the plain. The entire region drains into the East Sea (Sea of Japan) through the Songhua River, a major tributary of the Amur River of the Russian Far East.

Soils in the basin have been deposited from rivers and lakes throughout the Quaternary. These tend to be poorly drained, creating swampy, sometimes saline conditions in the low-lying areas. Boggy peat soils are present in some areas. Westward, this swampy landscape undergoes a transition to the drier steppes of the Hinggan foothills.

Icy flooded grasslands of the Nenjiang basin. @ C.Michael Hogan

The climate here is continental monsoon climate and is warmer and drier than in the surrounding mountains with mean annual precipitation of 400 to 450 millimeters (mm).

Typical vegetation in the lowlands of the Nenjiang River Basin consists of a distinctive coniferous swamp forest interspersed among meadows dominated by grasses and sedges. Forests are dominated by the Olga Bay Larch (Larix gmelini ssp. olgensis) which may grow through a lower story of Japanese White Birch (Betula platyphylla subsp. mandshurica). Meadows are dominated by grasses such as Feathertop Grass (Calamagrostis epigeios) and another Boreal Reed Grass, C. purpurea, that are adapted to grow in flooded soils. These often grow as dense tussocks that emerge from the flooded areas. Lakes are sometimes filled or lined at the margin by the salt-tolerant reed Phragmites australis.

The basin contains extensive flooded grassland areas, typified by the landscapes contained within its two largest nature reserves, Zhalong (in Heilongjiang Province) and Momoge (in Jilin Province). Among the flooded meadows are shallow, reed-filled lakes, rivers and old river courses undergoing ecological succession to grassland. Lakes may be either fresh or brackish, and salt concentrations are increasing in many areas as a result of freshwater diversions for agriculture.

Biodiversity features

Two large nature reserves protect wetland habitat in this ecoregion. Zhalong Nature Reserve (2100 square kilometres), located in the lower drainage basin of the Wuyur (Ulun) River, is a vast complex of permanent and seasonal freshwatermarshes with numerous shallow lakes and ponds and extensive reed beds (Phragmites spp.). There are a total of 303 recorded vertebrate species in the Nenjiang River grasslands ecoregion. Extensive flooding typically occurs during the spring and summer rainy season.

Avifauna

Zhalong serves as a wetland breeding area for bird species such as the rare Red-crowned Crane (Grus japonensis) and Chinese Merganser (Mergus squamatus). In addition to flooded grasslands, the reserve includes a network of freshwater reed marshes (400 square kilometres) that line or fill numerous small lakes and ponds. Natural lakes are mostly permanent freshwater, although some are seasonal or saline. During the April-June breeding season, productivity is high, with abundant fish, frogs, mollusks and aquatic insects, making this an ideal breeding area for waterfowl.

More than 200 bird species have been recorded in the Nenjiang River grasslands, including at least six of the world’s 15 crane species. The four species that breed here include Red-crowned Crane (Grus japonensis), White-necked Crane (G. vipio), Siberian Crane (G. leucogeranus), and Demoiselle crane (G. virgo), while two species stage here prior to migrating to their breeding habitat, the Common Crane (G. grus) and Hooded Crane (G. monacha). Other rare bird species that breed here are White Stork (Ciconia ciconia), Black Stork (C. nigra), Oriental white ibis (Threskiornis aethiopicus melanocephalus), Mandarin Duck (Aix galericulata), and Eurasian Spoonbill (Platalea leucorodia). This wetland habitat, together with the surrounding grassland, was declared a Ramsar site in 1992. It serves as a Chinese center for research on cranes, a bird revered in China as a symbol for long life.

Fish

Zhalong also supports 42 fish species. A few small nature reserves such as Heilonggong and Shanhe have been established to protect these species, as well as Rana amurensis.

Amphibians

A number of amphibians are found in the Nenjiang River grasslands, including the Asiatic Toad (Bufo gargarizans), typically found in flooded meadows; the Siberian Frog (Rana chensinensis), thought to hibernate underwater; Japanese Treefrog (Hyla japonica), an anuran who spawns in oxbow lakes and ponds; the Oriental Fire-bellied Toad (Bombina orientalis), found chiefly in mixed conifer-broadleaf forests. Zhalong also supports the amphibians Mongolian Toad (Pseudepidalea raddei) , European Treefrog (Hyla arborea), Black-spotted Frog (Pelophylax nigromaculatus)and R. temporaria. The Khabarovsk Frog, R. amurensis, is a protected anuran found in Zhalong.

Momoge Nature Reserve

Momoge Nature Reserve (1440 km2) serves as a breeding and staging ground for six crane species, an estimated 2000 individuals overall, including Red-crowned Crane, Siberian Crane, White-naped Crane and Demoiselle Crane. Other notable birds that breed here are the Great Bustard (Otis tarda) and White Stork (Ciconia ciconia). This site is thought to have potential for ecotourism and outdoor recreation, but is threatened by water pollution as well.

Ecoregion status

Satellite view of the grassland along the Nenjiang River, China. (Photograph by USGS)
The Zhalong Nature Reserve and other areas of wetland habitat in the Nenjiang River Basin have been threatened for many years by overfishing and encroachment by agriculture. However, many reserves have been put into place to protect the rare and endangered bird species of this ecoregion.

Types and severity of threats

Disruptive activities include collecting reeds, hunting, and collecting bird eggs. Salinisation has become a problem in some areas. This occurs when demand for irrigation water is so high that insufficient freshwater transits through the system to thoroughly flush out the salt. Industrial and tourism development also threatens some areas.

Petroleum and natural gas deposits provide one of China’s most productive oilfields here in the Songhua-Nenjiang Plain. The oil industry needs to be regulated very carefully, however, in order to be compatible with the wetland bird habitat.

General recommendations for nature reserves in this area are to control as best possible the water pollution caused by oil extraction, to prevent overfishing, to avoid dam construction, and attempt to develop tourism in a manner that is compatible with ecological integrity of these wetland areas.

Justification of ecoregion delineation

Due to the fertile soil in the region, the surrounding areas are intensively used for agriculture and thus the original extent of this ecoregion is difficult to estimate. Mapped ecoregion boundaries are derived from the Chinese Vegetation Map Compilation Committee saline meadow and flooded grassland along the Nenjiang River. Adjacent areas of annual cultivation are also included.

Disclaimer: This article contains some information that was originally published by the World Wildlife Fund. Topic editors and authors for the Encyclopedia of Earth have edited its content and added new information. The use of information from the World Wildlife Fund should not be construed as support for or endorsement by that organization for any new information added by EoE personnel, or for any editing of the original content.